Wrong usage of OffsetTime

[C-Otto]

Describe the bug
When determining the timezone offset for an image, exiftool-vendored uses the OffsetTime tag. This offset, however, corresponds to the file's modification date, not it's "original" date. As such, the timezone offset for images exported from (for example) Adobe Lightroom might be wrong.

Tag documentation: https://exiftool.org/TagNames/EXIF.html

To Reproduce
Example photo in immich-app/immich#12650 (comment)

{   
  "tz": "UTC+1",
  "tzSource": "OffsetTime",
   [...]
  "OffsetTime": "+01:00",
  "OffsetTimeOriginal": "+02:00",
  "OffsetTimeDigitized": "+02:00",
   [...]
}

This uses Immich's settings:

    defaultVideosToUTC: true,
    backfillTimezones: true,
    inferTimezoneFromDatestamps: true,
    inferTimezoneFromTimeStamp: true,
    useMWG: true,

Expected behavior
Timezone offset +02:00

Environment (please complete the following information):

• Version of this library: 28.7.0
• OS and version: Debian Stable
• Node.js version: 22.11.0